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Comment by alex_c | Hacker News Reader

The article doesn't spell it out, and I know practically nothing about the subject, but... what happens at the end of the 0.2s? Do the antimatter atoms drift out of the magnetic fields used to contain them? Do matter atoms drift in? Or is it some property of the atoms or magnetic fields? Basically, what needs to change to increase the 0.2s?

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Just based on what the article says, I suspect that even at the vacuum pressures they can achieve, there's enough normal matter around that eventually one of them penetrates the field and annihilates it.

Isn't the annihilation supposed to cause an explosion? How much energy is generated?

Isn't the annihilation supposed to cause an explosion?

It releases lots of energy proportional to the mass, yes, but one proton + one anti-proton annihilating at a time, it's a very small explosion. And they only had 38 anti-protons.

I believe that one of the the articles quotes one of the Physicists saying that it "wouldn't even warm up a cup of coffee"

Edit here you go:

Prof Rob Thompson, head of physics and astronomy at the University of Calgary, one of the 42 Alpha investigators, said: 'This is a major discovery. ... We've been able to trap about 38 atoms, which is an incredibly small amount, nothing like what we would need to power Star Trek's Starship Enterprise or even to heat a cup of coffee.'

Just take the resting mass of an hydrogen atom and multiply it by c^2. Try feeding Wolfram Alpha with "(mass of hydrogen) * (speed of light ^ 2)" or something, if you are lazy.

It's not very much in everyday units.

1 amu of anti-matter annihilates with 1 amu of matter and releases 0.3 nanoJoules of energy in the form of gamma rays. Or about 1.86 gigaelectronvolts (GeV, another unit of energy). In comparison, the particle collisions at the Large Hadron Collider occur at energies of about 14 TeV, or roughly 7,000 times more energetic, and occur numerous times per second.

They are neutral hydrogen atoms - why does a magnetic field affect them anyway?

The BBC article that's further down the front page at the moment brings it down closer to my level:

http://www.bbc.co.uk/news/science-environment-11773791

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"Atoms are neutral - they have no net charge - but they have a little magnetic character," explained Jeff Hangst of Aarhus University in Denmark, one of the collaborators on the Alpha antihydrogen trapping project.

"You can think of them as small compass needles, so they can be deflected using magnetic fields. We build a strong 'magnetic bottle' around where we produce the antihydrogen and, if they're not moving too quickly, they are trapped," he told BBC News.

Such sculpted magnetic fields that make up the magnetic bottle are not particularly strong, so the trick was to make antihydrogen atoms that didn't have much energy - that is, they were slow-moving.

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So, basically, magic. I'm just curious what the specific limitation is (but realize it may not be trivial to explain without understanding the entire containment process better).

Atomic clocks have the same problem. They use caesium atoms, which are hard to trap, and they want them moving very slowly so that thermal, doppler, and relativistic effects don't screw up the frequency signal you get from them. Hence caesium fountains, which fire the atoms upwards so that they come to the top of their gravitational parabola at about the time they drop a hyperfine energy level and emit the magic microwave photon.

Hydrogen (and anti-Hydrogen) is diamagnetic.

The link under further reading (http://cerncourier.com/cws/article/cern/30577) provides some insight.

Neutral atoms still have a magnetic moment. These do interact with magnetic fields. I'm way over my head here, so won't attempt to explain more.

http://en.wikipedia.org/wiki/Hyperfine_structure

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